Flow cytometry has become an indispensable tool for nearly all research involving functional, developmental and pathological aspects of cell biology. The goal of this application is to obtain the equipment (FACS Aria flow cytometer/cell sorter) necessary to provide active investigators at this institution with timely access to the state-of-the-art flow cytometry/cell sorting capabilities needed to support their ongoing and future research efforts. This institution has operated a Core Facility for Flow Cytometry since 1989, which was recently incorporated into a larger Research Core Facility. The success of flow cytometry on this campus (over 40 investigators are currently using this technology in some phase of their research) has led to a scarcity of available time for cell sorting experiments and a growing number of investigators requiring these services. Furthermore, our Research Core Facility needs to be able to supplement our existing equipment to take advantage of the recent advances in flow cytometric technology. The research applications to which this technology will be applied are very diverse in scope. Presented here are descriptions of research involving the studies of T cell development, B cell development, T cell function, T cell pathogenesis, cell trafficking, responses to viral infections and cellular analyses of genomic instability. All of the research described here have in common the need for timely access to flow cytometry/cell sorting as well as the increased optical sensitivity characteristic of the equipment requested. Additionally, several investigators require the ability to detect additional fluorochromes in the context of a single experiment and the ability to sort 4 populations simultaneously, rather than the 2 of which we are currently capable. As some of these research projects involve the use of potentially biohazardous agents such as the human pathogens HSV-1 and EBV, we will need to be able to safely sort viable cells that might harbor these agents. All of these capabilities are inherent in the equipment requested here. Thus, the availability of a new cell sorter on this campus is absolutely vital to the ongoing research efforts of these investigators and will provide adequate support for their future needs in the area of flow cytometry as well.